jai has asked for the wisdom of the Perl Monks concerning the following question:

Is there any regex to reverse the characters of a word ? Given text it should produce txet. I am trying to implement the linux command 'tac' in perl..
jai..

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Re: regex to reverse string
by broquaint (Abbot) on Aug 29, 2003 at 14:30 UTC
    Instead of a regex, just use reverse e.g 
    my $str = reverse 'a string';
print $str;

__output__

gnirts a

    [download]
    Make sure you're using it in scalar context though if you want to reverse a string. See. the reverse docs for more info.
    HTH

    _________
    broquaint

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Re: regex to reverse string
by diotalevi (Canon) on Aug 29, 2003 at 16:20 UTC

    Just to be perverse, here is exactly what you asked for

    print rx_reverse( shift );
sub rx_reverse {
    local $_ = shift;
    my $length = length;

    for my $offset ( 0 .. int($length / 2) ) {
        my $rx = rx_gen( $length, $offset );
        s/$rx/$1$4$3$2/;
    }
    $_
}

sub rx_gen {
    my $length = shift;
    my $offset = shift;
    my $skip = $length - 2 * ($offset + 1);
    return unless $length > 0 and
                  $offset <= ($length / 2) and
                  $skip >= 0;

    $offset = $offset ? "((?s:.){$offset})" : '()';
    $skip   = $skip   ? "((?s:.){$skip})"   : '()';
    return "^$offset((?s:.))$skip((?s:.))"
}

    [download]
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[d/l]
Re: regex to reverse string
by Zaxo (Archbishop) on Aug 29, 2003 at 14:33 UTC

    I think reverse in scalar context is what you want. 

    my $foo = 'text';
my $oof = reverse $foo;
print $oof, $/;

    [download]
    A regex might be possible but is unnecessary.

    After Compline,
    Zaxo

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[d/l]
Re: regex to reverse string
by Fletch (Bishop) on Aug 29, 2003 at 14:46 UTC
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(z) Re: regex to reverse string
by zigdon (Deacon) on Aug 29, 2003 at 14:35 UTC
    Any particular reason you want to use a regex? The reverse command might work for you:
    print scalar reverse $string;

    [download]

    -- zigdon

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Re: regex to reverse string
by antirice (Priest) on Aug 29, 2003 at 14:46 UTC

    <tongue_in_cheek>Sure, I'll bite: s/(.*)/reverse($1)/e </tongue_in_cheek>

    Hope this helps, although I doubt it will.

    antirice    
    The first rule of Perl club is - use Perl
    The     ith rule of Perl club is - follow rule i - 1 for i > 1

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Re: regex to reverse string
by artist (Parson) on Aug 29, 2003 at 16:26 UTC
    Now you can make practice of checking perldoc and find solution to many such problem along your journey.

    For your case check perldoc -q reverse or perldoc -f reverse.

    For more information, read perldoc perldoc.

    artist

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