I think I need to give everyone more to go on, so here it is. My matching code looks like the following.

while (content =~ m%One(.*?)three(.?)five\s+six(.*?)this%gs) {
$var1 = $1 ;
$var2 = $2 ;
$var3 = $3 ;
print "$var1\t$var2\t$var3\n" ;
}
[download]

It gives me output that looks like you would expect, say, for example:

When the code hangs, it prints out the same thing, but then nothing more.

Now, I've made the following change in keeping with your suggestion.

while (content =~ m%One(.*?)three(.?)five\s+six(.*?)this%gs) {
print(STDERR  "[", pos($content), "]") ;
$var1 = $1 ;
$var2 = $2 ;
$var3 = $3 ;
print "$var1\t$var2\t$var3\n" ;
}
[download]

I'm relatively new to PERL and not a professional coder, so I'm not sure what this is supposed to produce, but here's an example of what I am getting.

[
two   four   seven
48430]
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On another match, however, it gives me:

[48226]

three   more   numbers
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When it hangs, it gives me the following.

[50757]

first   three   numbers

second   three   numbers

third   three   numbers
[51826][52896]
[download]

Does this help with understanding the problem?

Why are you so reluctant to give us the regex (and not a similar regex), the data on which it hangs, and the rest of the program that might hang?

That leaves us pointlessly fishing in the fog.

"Sir, can you help me? my car is too slow" - "So, what kind of car is it?" - "a black one"

Sorry about that -- I am not a professional, so I guess I would get a bunch of grief for lack of elegance. Anyway, I would rather be embarrassed and have working code than not be embarrassed and have code that doesn't work. I included the code in another reply on this thread. Thanks.

Now, I've made the following change in keeping with your suggestion.

No you didn't. You moved the print statement.

Also, is that really the code you tested with?

while (content =~ m%One(.*?)three(.?)five\s+six(.*?)this%gs) {
       ^^^^^^^
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A function that's called over and over and over? I doubt you'd get the output you got if that was the case. Since you're showing us code that has no relevance to yours, it's hard to help.

If you try again, I'd switch to using the following:

$|=1;
while (
   print("[", pos($content), "]"),
   $content =~ m%One(.*?)three(.?)five\s+six(.*?)this%gs
) {
   $var1 = $1 ;
   $var2 = $2 ;
   $var3 = $3 ;
   print "$var1\t$var2\t$var3\n" ;
}
[download]

But an educated guess on what I've seen leads me to think it's not a problem with your loop.