Hi folks, Is there anyway to debug regular expressions?
I have a regex that resolves a lookahead expression at
the beginning of the expression. It looks like the
following 
( "hello Gags" =~ /^(?=hello).*[^G][^a].*$/ )&& print ("Matched") || p
+rint ("Unmatched")

[download]
Basically what it's saying is that if the engine looks
ahead from the start and locates the word 'hello'
then if the rest of the string DOES NOT contain the
char 'G' followed by the char 'a' then print matched or
else print unmatched.
i.e. for the above string it should return Unmatched... but
it doesn't.

Would anyone be able to tell me what the internal string
changes to after the engine reads (?=hello) and actually
locates the first hello?
Is there anyway to debug the resolution of regexes? I'm
using the debugger but it only does statements at a time.

Thanks,
Mark.

In reply to Debugging Regexes by perlgags78

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.