use Perl

• Use of // (Score:1)

  by swiftone (478)

  Okay, so Page 9 [perl.com] says that // is no longer a m//, but instead a short form of rx//.

  It also talks about delayed evaluation of the pattern.

  So, given that almost all the example patterns use /foo/ and not m/foo/, what is happening, and when is it happening?
  • Re:Use of // (Score:2)

    by Damian (784) on 2002.06.06 3:04 (#9244)

    So, given that almost all the example patterns use /foo/ and not m/foo/, what is
    happening, and when is it happening?
    
    /.../ now *always* returns a regex object.
    But a regex object in a void, boolean, string, numeric, or =~ context
    immediately matches against the current topic.
    
    So you get:

        /pattern/;                 # void context    -> automatch
        if /pattern/ {...}         # boolean context -> automatch
        %hash{/pattern/} = 1;      # string context  -> automatch
        if /pattern/ < 1 {...}     # numeric context -> automatch
        $str =~ /pattern/;         # =~ context      -> automatch
        when /pattern/ {...}       # =~ context      -> automatch

    and:

        @pats = (/pat1/, /pat2/);  # list context    -> no automatch
        %hash = ( pat => /pat/ );  # scalar context  -> no automatch
        $pat = /pat/;              # scalar context  -> no automatch
        given /pat/ {...}          # scalar context  -> no automatch

    And if you're ever unsure, just be explicit:

        $pat = rx/pat/;            # definitely assigning a regex object
        $pat = m /pat/;            # definitely assigning the match result

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