From your output it looks as if you want to replace the first occurrence of multiple zeros with a single zero, any subsequent multiple zero group should be left alone. This seems to work

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

print
   map { s{0{2,}}{0}; $_ }
   <DATA>;

__END__
215000007801
300000324002
890000457651
210004563401
201045139158

[download]

and the output is

21507801
30324002
890457651
2104563401
201045139158

[download]

I hope this is of use.

Cheers,

JohnGG

Update: Looks like I've misunderstood. If you say the first zero should not be touched, why does 890000457651 become 89457651 and not 890457651? Perhaps you could clarify what you require.

In reply to Re: Stuck in komplexer regex, at least for me by johngg
in thread Stuck in komplexer regex, at least for me by ultibuzz

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.