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Perl Language Reference Manual
by Larry Wall and others
Paperback (6"x9"), 724 pages
ISBN 9781906966027
RRP £29.95 ($39.95)

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=~ determines to which variable the regex is applied. In its absence, $_ is used.

$var =~ /foo/;

!~ determines to which variable the regex is applied, and negates the result of the match; it returns false if the match succeeds, and true if it fails.

$var !~ /foo/;

m/pattern/msixpogc searches a string for a pattern match, applying the given options.

m Multiline mode - ^ and $ match internal lines
s match as a Single line - . matches \n
i case-Insensitive
x eXtended legibility - free whitespace and comments
p Preserve a copy of the matched string - ${^PREMATCH}, ${^MATCH}, ${^POSTMATCH} will be defined.
o compile pattern Once
g Global - all occurrences
c don't reset pos on failed matches when using /g
If 'pattern' is an empty string, the last successfully matched regex is used. Delimiters other than '/' may be used for both this operator and the following ones. The leading m can be omitted if the delimiter is '/'. qr/pattern/msixpo lets you store a regex in a variable, or pass one around. Modifiers as for m//, and are stored within the regex. s/pattern/replacement/msixpogce substitutes matches of 'pattern' with 'replacement'. Modifiers as for m//, with one addition:
e Evaluate 'replacement' as an expression
'e' may be specified multiple times. 'replacement' is interpreted as a double quoted string unless a single-quote (') is the delimiter. ?pattern? is like m/pattern/ but matches only once. No alternate delimiters can be used. Must be reset with reset().
ISBN 9781906966027Perl Language Reference ManualSee the print edition