in reply to Re^2: How can I test for the representation of an integer?
in thread How can I test for the representation of an integer?

One is a match and the other is a count - you can tell that from the different ways you have constructed the regex. By choosing a confusing value to test against makes this less obvious. Instead try with "2":

$ perl -MData::Dumper -e 'print Dumper("2" =~ /2/);'
$VAR1 = 1;
$ perl -MData::Dumper -e 'print Dumper("2" =~ /(2)/);'
$VAR1 = '2';

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Re^4: How can I test for the representation of an integer?
by haukex (Archbishop) on Apr 25, 2016 at 11:43 UTC

    Hi hippo,

    I think you're thinking of s///g, since m// doesn't return a count (perlop):

    $ perl -MData::Dumper -e 'print Dumper(       "abbbbc"=~/b/    )'
$VAR1 = 1;
$ perl -MData::Dumper -e 'print Dumper(       "abbbbc"=~/(b)/  )'
$VAR1 = 'b';
$ perl -MData::Dumper -e 'print Dumper(scalar("abbbbc"=~/b/   ))'
$VAR1 = 1;
$ perl -MData::Dumper -e 'print Dumper(scalar("abbbbc"=~/(b)/ ))'
$VAR1 = 1;
$ perl -MData::Dumper -e 'print Dumper(scalar("abbbbc"=~/b/g  ))'
$VAR1 = 1;
$ perl -MData::Dumper -e 'print Dumper(scalar("abbbbc"=~/(b)/g))'
$VAR1 = 1;
$ perl -MData::Dumper -e 'print Dumper(       "abbbbc"=~/b/g   )'
$VAR1 = 'b';
$VAR2 = 'b';
$VAR3 = 'b';
$VAR4 = 'b';
$ perl -MData::Dumper -e 'print Dumper(       "abbbbc"=~/(b)/g )'
$VAR1 = 'b';
$VAR2 = 'b';
$VAR3 = 'b';
$VAR4 = 'b';

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    To get a count you need to use the =()= trick (perlsecret):

    $ perl -MData::Dumper -e 'print Dumper(scalar(()="abbbbc"=~/b/g))'
$VAR1 = 4;
$ perl -MData::Dumper -e 'print Dumper(scalar(()="abbbbc"=~/(b)/g))'
$VAR1 = 4;

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    Regards,
    -- Hauke D

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Re^4: How can I test for the representation of an integer?
by sm@sh (Acolyte) on Apr 25, 2016 at 11:14 UTC

    The regexps are user-supplied and arbitrary - they may or may not have captures.
    Matching the number '1' is a real use-case.

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      So I guess you want the count rather than the match (since you didn't specify). In that case, just force scalar context:

      $ perl -MData::Dumper -e 'print Dumper(scalar ("2" =~ /(2)/));'
$VAR1 = 1;

      [download]

      Update: As per haukex's correction the scalar context simply forces true/false rather than the count of matches. The above strategy still applies if this (whether the regex is a match or not) is all that you really want to test.

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