=head1 DESCRIPTION
-=head2 Operator Precedence and Associativity
+=head2 Operator Precedence and Associativity
X<operator, precedence> X<precedence> X<associativity>
Operator precedence and associativity work in Perl more or less like
print ++$j; # prints 1
Note that just as in C, Perl doesn't define B<when> the variable is
-incremented or decremented. You just know it will be done sometime
+incremented or decremented. You just know it will be done sometime
before or after the value is returned. This also means that modifying
a variable twice in the same statement will lead to undefined behaviour.
Avoid statements like:
supposed to be searched, substituted, or transliterated instead of the default
$_. When used in scalar context, the return value generally indicates the
success of the operation. Behavior in list context depends on the particular
-operator. See L</"Regexp Quote-Like Operators"> for details and
+operator. See L</"Regexp Quote-Like Operators"> for details and
L<perlretut> for examples using these operators.
If the right argument is an expression rather than a search pattern,
substitution, or transliteration, it is interpreted as a search pattern at run
-time.
+time. Note that this means that its contents will be interpolated twice, so
+
+ '\\' =~ q'\\';
+
+is not ok, as the regex engine will end up trying to compile the
+pattern C<\>, which it will consider a syntax error.
Binary "!~" is just like "=~" except the return value is negated in
the logical sense.
C<$a>. If C<$b> is negative, then C<$a % $b> is C<$a> minus the
smallest multiple of C<$b> that is not less than C<$a> (i.e. the
result will be less than or equal to zero). If the operands
-C<$a> and C<$b> are floting point values, only the integer portion
-of C<$a> and C<$b> will be used in the operation.
+C<$a> and C<$b> are floating point values and the absolute value of
+C<$b> (that is C<abs($b)>) is less than C<(UV_MAX + 1)>, only
+the integer portion of C<$a> and C<$b> will be used in the operation
+(Note: here C<UV_MAX> means the maximum of the unsigned integer type).
+If the absolute value of the right operand (C<abs($b)>) is greater than
+or equal to C<(UV_MAX + 1)>, "%" computes the floating-point remainder
+C<$r> in the equation C<($r = $a - $i*$b)> where C<$i> is a certain
+integer that makes C<$r> should have the same sign as the right operand
+C<$b> (B<not> as the left operand C<$a> like C function C<fmod()>)
+and the absolute value less than that of C<$b>.
Note that when C<use integer> is in scope, "%" gives you direct access
to the modulus operator as implemented by your C compiler. This
operator is not as well defined for negative operands, but it will
X<cmp>
Binary "~~" does a smart match between its arguments. Smart matching
-is described in L<perlsyn/"Smart Matching in Detail">.
+is described in L<perlsyn/"Smart matching in detail">.
This operator is only available if you enable the "~~" feature:
see L<feature> for more information.
X<~~>
X<//> X<operator, logical, defined-or>
Although it has no direct equivalent in C, Perl's C<//> operator is related
-to its C-style or. In fact, it's exactly the same as C<||>, except that it
+to its C-style or. In fact, it's exactly the same as C<||>, except that it
tests the left hand side's definedness instead of its truth. Thus, C<$a // $b>
-is similar to C<defined($a) || $b> (except that it returns the value of C<$a>
-rather than the value of C<defined($a)>) and is exactly equivalent to
+is similar to C<defined($a) || $b> (except that it returns the value of C<$a>
+rather than the value of C<defined($a)>) and is exactly equivalent to
C<defined($a) ? $a : $b>. This is very useful for providing default values
-for variables. If you actually want to test if at least one of C<$a> and
+for variables. If you actually want to test if at least one of C<$a> and
C<$b> is defined, use C<defined($a // $b)>.
The C<||>, C<//> and C<&&> operators return the last value evaluated
As more readable alternatives to C<&&>, C<//> and C<||> when used for
control flow, Perl provides C<and>, C<err> and C<or> operators (see below).
-The short-circuit behavior is identical. The precedence of "and", "err"
+The short-circuit behavior is identical. The precedence of "and", "err"
and "or" is much lower, however, so that you can safely use them after a
list operator without the need for parentheses:
=back
=head2 Quote and Quote-like Operators
-X<operator, quote> X<operator, quote-like> X<q> X<qq> X<qx> X<qw> X<m>
+X<operator, quote> X<operator, quote-like> X<q> X<qq> X<qx> X<qw> X<m>
X<qr> X<s> X<tr> X<'> X<''> X<"> X<""> X<//> X<`> X<``> X<<< << >>>
X<escape sequence> X<escape>
Interpolating an array or slice interpolates the elements in order,
separated by the value of C<$">, so is equivalent to interpolating
-C<join $", @array>. "Punctuation" arrays such as C<@+> are only
-interpolated if the name is enclosed in braces C<@{+}>.
+C<join $", @array>. "Punctuation" arrays such as C<@*> are only
+interpolated if the name is enclosed in braces C<@{*}>, but special
+arrays C<@_>, C<@+>, and C<@-> are interpolated, even without braces.
-You cannot include a literal C<$> or C<@> within a C<\Q> sequence.
-An unescaped C<$> or C<@> interpolates the corresponding variable,
+You cannot include a literal C<$> or C<@> within a C<\Q> sequence.
+An unescaped C<$> or C<@> interpolates the corresponding variable,
while escaping will cause the literal string C<\$> to be inserted.
-You'll need to write something like C<m/\Quser\E\@\Qhost/>.
+You'll need to write something like C<m/\Quser\E\@\Qhost/>.
Patterns are subject to an additional level of interpretation as a
regular expression. This is done as a second pass, after variables are
around the year 2168.
=item m/PATTERN/cgimosx
-X<m> X<operator, match>
-X<regexp, options> X<regexp> X<regex, options> X<regex>
+X<m> X<operator, match>
+X<regexp, options> X<regexp> X<regex, options> X<regex>
X</c> X</i> X</m> X</o> X</s> X</x>
-=item /PATTERN/cgimosx
+=item /PATTERN/cgimosxk
Searches a string for a pattern match, and in scalar context returns
true if it succeeds, false if it fails. If no string is specified
Options are:
- c Do not reset search position on a failed match when /g is in effect.
- g Match globally, i.e., find all occurrences.
i Do case-insensitive pattern matching.
m Treat string as multiple lines.
- o Compile pattern only once.
s Treat string as single line.
x Use extended regular expressions.
+ g Match globally, i.e., find all occurrences.
+ c Do not reset search position on a failed match when /g is in effect.
+ o Compile pattern only once.
+ k Keep a copy of the matched string so that ${^MATCH} and friends
+ will be defined.
If "/" is the delimiter then the initial C<m> is optional. With the C<m>
-you can use any pair of non-alphanumeric, non-whitespace characters
+you can use any pair of non-alphanumeric, non-whitespace characters
as delimiters. This is particularly useful for matching path names
that contain "/", to avoid LTS (leaning toothpick syndrome). If "?" is
the delimiter, then the match-only-once rule of C<?PATTERN?> applies.
previously succeeded, this will (silently) act instead as a genuine
empty pattern (which will always match).
-Note that it's possible to confuse Perl into thinking C<//> (the empty
-regex) is really C<//> (the defined-or operator). Perl is usually pretty
-good about this, but some pathological cases might trigger this, such as
-C<$a///> (is that C<($a) / (//)> or C<$a // />?) and C<print $fh //>
-(C<print $fh(//> or C<print($fh //>?). In all of these examples, Perl
-will assume you meant defined-or. If you meant the empty regex, just
-use parentheses or spaces to disambiguate, or even prefix the empty
+Note that it's possible to confuse Perl into thinking C<//> (the empty
+regex) is really C<//> (the defined-or operator). Perl is usually pretty
+good about this, but some pathological cases might trigger this, such as
+C<$a///> (is that C<($a) / (//)> or C<$a // />?) and C<print $fh //>
+(C<print $fh(//> or C<print($fh //>?). In all of these examples, Perl
+will assume you meant defined-or. If you meant the empty regex, just
+use parentheses or spaces to disambiguate, or even prefix the empty
regex with an C<m> (so C<//> becomes C<m//>).
If the C</g> option is not used, C<m//> in list context returns a
regexp tries to match where the previous one leaves off.
$_ = <<'EOL';
- $url = new URI::URL "http://www/"; die if $url eq "xXx";
+ $url = URI::URL->new( "http://www/" ); die if $url eq "xXx";
EOL
LOOP:
{
A common mistake is to try to separate the words with comma or to
put comments into a multi-line C<qw>-string. For this reason, the
-C<use warnings> pragma and the B<-w> switch (that is, the C<$^W> variable)
+C<use warnings> pragma and the B<-w> switch (that is, the C<$^W> variable)
produces warnings if the STRING contains the "," or the "#" character.
-=item s/PATTERN/REPLACEMENT/egimosx
+=item s/PATTERN/REPLACEMENT/egimosxk
X<substitute> X<substitution> X<replace> X<regexp, replace>
X<regexp, substitute> X</e> X</g> X</i> X</m> X</o> X</s> X</x>
Options are:
- e Evaluate the right side as an expression.
- g Replace globally, i.e., all occurrences.
i Do case-insensitive pattern matching.
m Treat string as multiple lines.
- o Compile pattern only once.
s Treat string as single line.
x Use extended regular expressions.
+ g Replace globally, i.e., all occurrences.
+ o Compile pattern only once.
+ k Keep a copy of the original string so ${^MATCH} and friends
+ will be defined.
+ e Evaluate the right side as an expression.
+
Any non-alphanumeric, non-whitespace delimiter may replace the
slashes. If single quotes are used, no interpretation is done on the
s/%(.)/$percent{$1}/g; # change percent escapes; no /e
s/%(.)/$percent{$1} || $&/ge; # expr now, so /e
- s/^=(\w+)/&pod($1)/ge; # use function call
+ s/^=(\w+)/pod($1)/ge; # use function call
# expand variables in $_, but dynamics only, using
# symbolic dereferencing
to occur that you might want. Here are two common cases:
# put commas in the right places in an integer
- 1 while s/(\d)(\d\d\d)(?!\d)/$1,$2/g;
+ 1 while s/(\d)(\d\d\d)(?!\d)/$1,$2/g;
# expand tabs to 8-column spacing
1 while s/\t+/' ' x (length($&)*8 - length($`)%8)/e;
string specified with =~ must be a scalar variable, an array element, a
hash element, or an assignment to one of those, i.e., an lvalue.)
-A character range may be specified with a hyphen, so C<tr/A-J/0-9/>
+A character range may be specified with a hyphen, so C<tr/A-J/0-9/>
does the same replacement as C<tr/ACEGIBDFHJ/0246813579/>.
For B<sed> devotees, C<y> is provided as a synonym for C<tr>. If the
SEARCHLIST is delimited by bracketing quotes, the REPLACEMENTLIST has
e.g., C<tr[A-Z][a-z]> or C<tr(+\-*/)/ABCD/>.
Note that C<tr> does B<not> do regular expression character classes
-such as C<\d> or C<[:lower:]>. The <tr> operator is not equivalent to
+such as C<\d> or C<[:lower:]>. The C<tr> operator is not equivalent to
the tr(1) utility. If you want to map strings between lower/upper
cases, see L<perlfunc/lc> and L<perlfunc/uc>, and in general consider
using the C<s> operator if you need regular expressions.
A line-oriented form of quoting is based on the shell "here-document"
syntax. Following a C<< << >> you specify a string to terminate
the quoted material, and all lines following the current line down to
-the terminating string are the value of the item. The terminating
-string may be either an identifier (a word), or some quoted text. If
-quoted, the type of quotes you use determines the treatment of the
-text, just as in regular quoting. An unquoted identifier works like
-double quotes. There must be no space between the C<< << >> and
-the identifier, unless the identifier is quoted. (If you put a space it
-will be treated as a null identifier, which is valid, and matches the first
-empty line.) The terminating string must appear by itself (unquoted and
-with no surrounding whitespace) on the terminating line.
+the terminating string are the value of the item.
+
+The terminating string may be either an identifier (a word), or some
+quoted text. An unquoted identifier works like double quotes.
+There may not be a space between the C<< << >> and the identifier,
+unless the identifier is explicitly quoted. (If you put a space it
+will be treated as a null identifier, which is valid, and matches the
+first empty line.) The terminating string must appear by itself
+(unquoted and with no surrounding whitespace) on the terminating line.
+
+If the terminating string is quoted, the type of quotes used determine
+the treatment of the text.
+
+=over 4
+
+=item Double Quotes
+
+Double quotes indicate that the text will be interpolated using exactly
+the same rules as normal double quoted strings.
print <<EOF;
The price is $Price.
The price is $Price.
EOF
- print << `EOC`; # execute commands
+
+=item Single Quotes
+
+Single quotes indicate the text is to be treated literally with no
+interpolation of its content. This is similar to single quoted
+strings except that backslashes have no special meaning, with C<\\>
+being treated as two backslashes and not one as they would in every
+other quoting construct.
+
+This is the only form of quoting in perl where there is no need
+to worry about escaping content, something that code generators
+can and do make good use of.
+
+=item Backticks
+
+The content of the here doc is treated just as it would be if the
+string were embedded in backticks. Thus the content is interpolated
+as though it were double quoted and then executed via the shell, with
+the results of the execution returned.
+
+ print << `EOC`; # execute command and get results
echo hi there
- echo lo there
EOC
+=back
+
+It is possible to stack multiple here-docs in a row:
+
print <<"foo", <<"bar"; # you can stack them
I said foo.
foo
ABC
+ 20;
-If you want your here-docs to be indented with the
-rest of the code, you'll need to remove leading whitespace
-from each line manually:
+If you want to remove the line terminator from your here-docs,
+use C<chomp()>.
+
+ chomp($string = <<'END');
+ This is a string.
+ END
+
+If you want your here-docs to be indented with the rest of the code,
+you'll need to remove leading whitespace from each line manually:
($quote = <<'FINIS') =~ s/^\s+//gm;
- The Road goes ever on and on,
+ The Road goes ever on and on,
down from the door where it began.
FINIS
you have to write
- s/this/<<E . 'that'
- . 'more '/eg;
- the other
- E
+ s/this/<<E . 'that'
+ . 'more '/eg;
+ the other
+ E
If the terminating identifier is on the last line of the program, you
must be sure there is a newline after it; otherwise, Perl will give the
warning B<Can't find string terminator "END" anywhere before EOF...>.
-Additionally, the quoting rules for the identifier are not related to
-Perl's quoting rules -- C<q()>, C<qq()>, and the like are not supported
-in place of C<''> and C<"">, and the only interpolation is for backslashing
-the quoting character:
+Additionally, the quoting rules for the end of string identifier are not
+related to Perl's quoting rules -- C<q()>, C<qq()>, and the like are not
+supported in place of C<''> and C<"">, and the only interpolation is for
+backslashing the quoting character:
print << "abc\"def";
testing...
Some passes discussed below are performed concurrently, but because
their results are the same, we consider them individually. For different
quoting constructs, Perl performs different numbers of passes, from
-one to five, but these passes are always performed in the same order.
+one to four, but these passes are always performed in the same order.
=over 4
=item Finding the end
-The first pass is finding the end of the quoted construct, whether
-it be a multicharacter delimiter C<"\nEOF\n"> in the C<<<EOF>
-construct, a C</> that terminates a C<qq//> construct, a C<]> which
-terminates C<qq[]> construct, or a C<< > >> which terminates a
-fileglob started with C<< < >>.
-
-When searching for single-character non-pairing delimiters, such
-as C</>, combinations of C<\\> and C<\/> are skipped. However,
-when searching for single-character pairing delimiter like C<[>,
-combinations of C<\\>, C<\]>, and C<\[> are all skipped, and nested
-C<[>, C<]> are skipped as well. When searching for multicharacter
-delimiters, nothing is skipped.
+The first pass is finding the end of the quoted construct, where
+the information about the delimiters is used in parsing.
+During this search, text between the starting and ending delimiters
+is copied to a safe location. The text copied gets delimiter-independent.
+
+If the construct is a here-doc, the ending delimiter is a line
+that has a terminating string as the content. Therefore C<<<EOF> is
+terminated by C<EOF> immediately followed by C<"\n"> and starting
+from the first column of the terminating line.
+When searching for the terminating line of a here-doc, nothing
+is skipped. In other words, lines after the here-doc syntax
+are compared with the terminating string line by line.
+
+For the constructs except here-docs, single characters are used as starting
+and ending delimiters. If the starting delimiter is an opening punctuation
+(that is C<(>, C<[>, C<{>, or C<< < >>), the ending delimiter is the
+corresponding closing punctuation (that is C<)>, C<]>, C<}>, or C<< > >>).
+If the starting delimiter is an unpaired character like C</> or a closing
+punctuation, the ending delimiter is same as the starting delimiter.
+Therefore a C</> terminates a C<qq//> construct, while a C<]> terminates
+C<qq[]> and C<qq]]> constructs.
+
+When searching for single-character delimiters, escaped delimiters
+and C<\\> are skipped. For example, while searching for terminating C</>,
+combinations of C<\\> and C<\/> are skipped. If the delimiters are
+bracketing, nested pairs are also skipped. For example, while searching
+for closing C<]> paired with the opening C<[>, combinations of C<\\>, C<\]>,
+and C<\[> are all skipped, and nested C<[> and C<]> are skipped as well.
+However, when backslashes are used as the delimiters (like C<qq\\> and
+C<tr\\\>), nothing is skipped.
+During the search for the end, backslashes that escape delimiters
+are removed (exactly speaking, they are not copied to the safe location).
For constructs with three-part delimiters (C<s///>, C<y///>, and
C<tr///>), the search is repeated once more.
+If the first delimiter is not an opening punctuation, three delimiters must
+be same such as C<s!!!> and C<tr)))>, in which case the second delimiter
+terminates the left part and starts the right part at once.
+If the left part is delimited by bracketing punctuations (that is C<()>,
+C<[]>, C<{}>, or C<< <> >>), the right part needs another pair of
+delimiters such as C<s(){}> and C<tr[]//>. In these cases, whitespaces
+and comments are allowed between both parts, though the comment must follow
+at least one whitespace; otherwise a character expected as the start of
+the comment may be regarded as the starting delimiter of the right part.
During this search no attention is paid to the semantics of the construct.
Thus:
or:
- m/
+ m/
bar # NOT a comment, this slash / terminated m//!
/x
the example above is not C<m//x>, but rather C<m//> with no C</x>
modifier. So the embedded C<#> is interpreted as a literal C<#>.
-Also no attention is paid to C<\c\> during this search.
-Thus the second C<\> in C<qq/\c\/> is interpreted as a part of C<\/>,
-and the following C</> is not recognized as a delimiter.
+Also no attention is paid to C<\c\> (multichar control char syntax) during
+this search. Thus the second C<\> in C<qq/\c\/> is interpreted as a part
+of C<\/>, and the following C</> is not recognized as a delimiter.
Instead, use C<\034> or C<\x1c> at the end of quoted constructs.
-=item Removal of backslashes before delimiters
-
-During the second pass, text between the starting and ending
-delimiters is copied to a safe location, and the C<\> is removed
-from combinations consisting of C<\> and delimiter--or delimiters,
-meaning both starting and ending delimiters will should these differ.
-This removal does not happen for multi-character delimiters.
-Note that the combination C<\\> is left intact, just as it was.
-
-Starting from this step no information about the delimiters is
-used in parsing.
-
=item Interpolation
X<interpolation>
The next step is interpolation in the text obtained, which is now
-delimiter-independent. There are four different cases.
+delimiter-independent. There are multiple cases.
=over 4
-=item C<<<'EOF'>, C<m''>, C<s'''>, C<tr///>, C<y///>
+=item C<<<'EOF'>
No interpolation is performed.
+Note that the combination C<\\> is left intact, since escaped delimiters
+are not available for here-docs.
+
+=item C<m''>, the pattern of C<s'''>
+
+No interpolation is performed at this stage.
+Any backslashed sequences including C<\\> are treated at the stage
+to L</"parsing regular expressions">.
+
+=item C<''>, C<q//>, C<tr'''>, C<y'''>, the replacement of C<s'''>
+
+The only interpolation is removal of C<\> from pairs of C<\\>.
+Therefore C<-> in C<tr'''> and C<y'''> is treated literally
+as a hyphen and no character range is available.
+C<\1> in the replacement of C<s'''> does not work as C<$1>.
-=item C<''>, C<q//>
+=item C<tr///>, C<y///>
-The only interpolation is removal of C<\> from pairs C<\\>.
+No variable interpolation occurs. String modifying combinations for
+case and quoting such as C<\Q>, C<\U>, and C<\E> are not recognized.
+The other escape sequences such as C<\200> and C<\t> and backslashed
+characters such as C<\\> and C<\-> are converted to appropriate literals.
+The character C<-> is treated specially and therefore C<\-> is treated
+as a literal C<->.
-=item C<"">, C<``>, C<qq//>, C<qx//>, C<< <file*glob> >>
+=item C<"">, C<``>, C<qq//>, C<qx//>, C<< <file*glob> >>, C<<<"EOF">
C<\Q>, C<\U>, C<\u>, C<\L>, C<\l> (possibly paired with C<\E>) are
converted to corresponding Perl constructs. Thus, C<"$foo\Qbaz$bar">
is converted to C<$foo . (quotemeta("baz" . $bar))> internally.
-The other combinations are replaced with appropriate expansions.
+The other escape sequences such as C<\200> and C<\t> and backslashed
+characters such as C<\\> and C<\-> are replaced with appropriate
+expansions.
Let it be stressed that I<whatever falls between C<\Q> and C<\E>>
is interpolated in the usual way. Something like C<"\Q\\E"> has
scalar.
Note also that the interpolation code needs to make a decision on
-where the interpolated scalar ends. For instance, whether
+where the interpolated scalar ends. For instance, whether
C<< "a $b -> {c}" >> really means:
"a " . $b . " -> {c}";
on heuristic estimators, the result is not strictly predictable.
Fortunately, it's usually correct for ambiguous cases.
-=item C<?RE?>, C</RE/>, C<m/RE/>, C<s/RE/foo/>,
+=item the replacement of C<s///>
Processing of C<\Q>, C<\U>, C<\u>, C<\L>, C<\l>, and interpolation
-happens (almost) as with C<qq//> constructs, but the substitution
-of C<\> followed by RE-special chars (including C<\>) is not
-performed. Moreover, inside C<(?{BLOCK})>, C<(?# comment )>, and
+happens as with C<qq//> constructs.
+
+It is at this step that C<\1> is begrudgingly converted to C<$1> in
+the replacement text of C<s///>, in order to correct the incorrigible
+I<sed> hackers who haven't picked up the saner idiom yet. A warning
+is emitted if the C<use warnings> pragma or the B<-w> command-line flag
+(that is, the C<$^W> variable) was set.
+
+=item C<RE> in C<?RE?>, C</RE/>, C<m/RE/>, C<s/RE/foo/>,
+
+Processing of C<\Q>, C<\U>, C<\u>, C<\L>, C<\l>, C<\E>,
+and interpolation happens (almost) as with C<qq//> constructs.
+
+However any other combinations of C<\> followed by a character
+are not substituted but only skipped, in order to parse them
+as regular expressions at the following step.
+As C<\c> is skipped at this step, C<@> of C<\c@> in RE is possibly
+treated as an array symbol (for example C<@foo>),
+even though the same text in C<qq//> gives interpolation of C<\c@>.
+
+Moreover, inside C<(?{BLOCK})>, C<(?# comment )>, and
a C<#>-comment in a C<//x>-regular expression, no processing is
performed whatsoever. This is the first step at which the presence
of the C<//x> modifier is relevant.
-Interpolation has several quirks: C<$|>, C<$(>, and C<$)> are not
-interpolated, and constructs C<$var[SOMETHING]> are voted (by several
-different estimators) to be either an array element or C<$var>
-followed by an RE alternative. This is where the notation
+Interpolation in patterns has several quirks: C<$|>, C<$(>, C<$)>, C<@+>
+and C<@-> are not interpolated, and constructs C<$var[SOMETHING]> are
+voted (by several different estimators) to be either an array element
+or C<$var> followed by an RE alternative. This is where the notation
C<${arr[$bar]}> comes handy: C</${arr[0-9]}/> is interpreted as
array element C<-9>, not as a regular expression from the variable
C<$arr> followed by a digit, which would be the interpretation of
C</$arr[0-9]/>. Since voting among different estimators may occur,
the result is not predictable.
-It is at this step that C<\1> is begrudgingly converted to C<$1> in
-the replacement text of C<s///> to correct the incorrigible
-I<sed> hackers who haven't picked up the saner idiom yet. A warning
-is emitted if the C<use warnings> pragma or the B<-w> command-line flag
-(that is, the C<$^W> variable) was set.
-
The lack of processing of C<\\> creates specific restrictions on
the post-processed text. If the delimiter is C</>, one cannot get
the combination C<\/> into the result of this step. C</> will
m m ^ a \s* b mmx;
In the RE above, which is intentionally obfuscated for illustration, the
-delimiter is C<m>, the modifier is C<mx>, and after backslash-removal the
-RE is the same as for C<m/ ^ a \s* b /mx>. There's more than one
+delimiter is C<m>, the modifier is C<mx>, and after delimiter-removal the
+RE is the same as for C<m/ ^ a \s* b /mx>. There's more than one
reason you're encouraged to restrict your delimiters to non-alphanumeric,
non-whitespace choices.
This step is the last one for all constructs except regular expressions,
which are processed further.
-=item Interpolation of regular expressions
-X<regexp, interpolation>
+=item parsing regular expressions
+X<regexp, parse>
Previous steps were performed during the compilation of Perl code,
but this one happens at run time--although it may be optimized to
be calculated at compile time if appropriate. After preprocessing
-described above, and possibly after evaluation if catenation,
+described above, and possibly after evaluation if concatenation,
joining, casing translation, or metaquoting are involved, the
resulting I<string> is passed to the RE engine for compilation.
This also behaves similarly, but avoids $_ :
- while (my $line = <STDIN>) { print $line }
+ while (my $line = <STDIN>) { print $line }
In these loop constructs, the assigned value (whether assignment
is automatic or explicit) is then tested to see whether it is
while (<STDIN>) { last unless $_; ... }
In other boolean contexts, C<< <I<filehandle>> >> without an
-explicit C<defined> test or comparison elicit a warning if the
+explicit C<defined> test or comparison elicit a warning if the
C<use warnings> pragma or the B<-w>
command-line switch (the C<$^W> variable) is in effect.
continue as though the input were one big happy file. See the example
in L<perlfunc/eof> for how to reset line numbers on each file.
-If you want to set @ARGV to your own list of files, go right ahead.
+If you want to set @ARGV to your own list of files, go right ahead.
This sets @ARGV to all plain text files if no @ARGV was given:
@ARGV = grep { -f && -T } glob('*') unless @ARGV;
# ... # code for each line
}
-The <> symbol will return C<undef> for end-of-file only once.
-If you call it again after this, it will assume you are processing another
+The <> symbol will return C<undef> for end-of-file only once.
+If you call it again after this, it will assume you are processing another
@ARGV list, and if you haven't set @ARGV, will read input from STDIN.
If what the angle brackets contain is a simple scalar variable (e.g.,
The granularity for such extension or truncation is one or more
bytes.
- # ASCII-based examples
+ # ASCII-based examples
print "j p \n" ^ " a h"; # prints "JAPH\n"
print "JA" | " ph\n"; # prints "japh\n"
print "japh\nJunk" & '_____'; # prints "JAPH\n";
or so.
Used on numbers, the bitwise operators ("&", "|", "^", "~", "<<",
-and ">>") always produce integral results. (But see also
+and ">>") always produce integral results. (But see also
L<Bitwise String Operators>.) However, C<use integer> still has meaning for
them. By default, their results are interpreted as unsigned integers, but
if C<use integer> is in effect, their results are interpreted
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