Congratulations. That is a handy function. Here are some suggestions.

for(0..100) {
    sleep .15;
}
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In my machine, this takes nowhere near 15 seconds to run. Why? Because it is identical to:

for(0..100) {
    sleep 0;
}
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The standard FAQs have information on how to sleep for less than 1 second. Now that Perl worked around a "bug" in Win32 select(), your best bet is:

    my( $x, $y, $z );
    select($x=undef,$y=undef,$z=undef,0.15);
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You don't exit the loop once the flock succeeds. I'd just to a return 1 if flock... and drop the whole $locked variable.

You might want to get into the habbit of using #!/usr/bin/perl -w and use strict;, since they will probably eventually save you a lot of time debugging.

I'd replace the print...exit part with a call to die since that will allow your callers to trap failure if they want to.

And don't worry too much about errors. We all make errors. That is one of the most common ways to learn new things.

Besides, none of my suggestions point out what I would call "show stoppers".