in reply to printing LAST_MATCH_START/@- LAST_MATCH_END/@+ array where regex match begin/end

Move the match with /g into a condition of a while loop.

As there are no capture groups in the regex (i.e. no parentheses), using any other index than 0 makes no sense. Under warnings, you'd even get lots of Use of uninitialized value in print.

Moreover, when there's no match, the @- and @+ arrays are empty, there's no -1 (that's what index does). You have to handle that case yourself.

This should work directly as shown and output the expected output:

#!/usr/bin/perl
use strict;
use warnings;

my $string = << "__EOS__";
foo bar baz
foo bar foo\tbaz ccc ddd
foo bar foo\tbaz ccc ddd\tfoo\tbar\tbaz
foo bar foo\t\tbaz ccc ddd\t\t\tfoo
__EOS__

open my $F0, '<', \$string or die $!;

while (<$F0>) {
    my $match;
    while (/\t+/g) {
        $match = 1;
        print  $-[0], ' ', $+[0], ' ';
    }
    print '-1 -1' unless $match;
    print "\n";
}

[download]

map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

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Re^2: printing LAST_MATCH_START/@- LAST_MATCH_END/@+ array where regex match begin/end
by perl_boy (Novice) on Dec 29, 2021 at 00:57 UTC
    thank's for the tip. I have replaced the code inside the while loop with code you provided 
    open(F0, $ARGV[0]);

while(<F0>) {
    my $match;
    while (/\t+/g) {
        $match = 1;
        print  $-[0], ' ', $+[0], ' ';
    }
    print '-1 -1' unless $match;
    print "\n";
}

close F0;

    [download]
    and works fine and get the expected results. good thank's :)))

    However I find that that PerlDoc https://perldoc.perl.org/perlvar#Variables-related-to-regular-expressions
    is a bit misleading when it says that indexes/positions before and after regex match can be found in the LAST_MATCH_START/@- and LAST_MATCH_END/@+ array by printing
    print  $+[0], " ",$+[1], " ", $+[2], "\n" ;

    [download]

    again thank's for the code :)))
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