in reply to Get regexp modifiers

I've got the gut-feeling, that this is bad advice and there's a better way to do it... but the following works here... 

use strict;

# print RE into variable and examine it...
sub is_ci {
    my $check_re = shift;

    die "$check_re is not a RE" if ref $check_re ne 'Regexp';

    open my $redir , '>', \my $output; 
    print $redir $check_re; 
    close $redir;

    return $output =~ /i.*?\-/; # i before '-' 
}


my $r1 = qr/hello/i;
my $r2 = qr/hello/;

print "true  is " ,  is_ci($r1) ? 'true' : 'false' , " ?\n"; # true
print "false is " ,  is_ci($r2) ? 'true' : 'false' , " ?\n"; # false
print "false is " ,  is_ci(\"nonsense") ? 'true' : 'false' , " ?\n"; #
+ die!

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HTH

Update: Ah trustworthy guts ;-) See ikegamis response below...

Reading this thread, I second what ww questions here - if one needs to check regexp modifiers a posteriori, that seems to be an indicator for a design problem. But maybe the regexp comes from user input... ?

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Re^2: Get regexp modifiers
by ikegami (Patriarch) on Jan 06, 2010 at 02:15 UTC

    I think ref($check_re) ne 'Regexp' can fail in modern Perls. You want to use 

    use re qw( is_regexp );
is_regexp($check_re)

    [download]
    Or if you want to support Perl < 5.10, 
    BEGIN {
   eval 'use re qw( is_regexp )';
   if (!defined(&is_regexp)) {
      my $re_class = ref qr//;
      *is_regexp = sub($) {
         local *__ANON__ = 'is_regexp';
         return UNIVERSAL::isa($_[0], $re_class);
      };
   }
}

is_regexp($check_re)

    [download]

    That said, I don't think you should be checking if it's a compiled regex pattern at all. Just checking if it looks like one (as I did) is much more tolerant.

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[d/l]
[select]
      I think ref($check_re) ne 'Regexp' can fail in modern Perls.

      Could you explain that? (Or post a link to the relevant documentation?)

      Alexander

      --
      Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)
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[d/l]
        ./perl -Ilib -le'
    my $r = ${ qr/abc/ };
    print $r;
    print ref($r)           ?1:0;
    print re::is_regexp($r) ?1:0;
    print "abc" =~ $r       ?1:0;
'
(?-xism:abc)
0
1
1

        [download]

        "sufficiently modern" appears to mean ≥5.12 in this case

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[d/l]

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