Your problem is elsewhere. The . was not removed by that regexp. Or maybe you're not using strict (bad!) and really did forget to put the quotes around YYYYMMDD_something.xyz. 
my $filename = 'YYYYMMDD_something.xyz';
my $DATE     = '20061124';
$filename =~ s/YYYYMMDD/$DATE/i;
print($filename, "\n");  # 20061124_something.xyz

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In reply to Re: Quick question on regex by ikegami
in thread Quick question on regex by narashima

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