Hi :)
It was $t which was causing the problem.I had declared it using

my $t = $mw->Scrolled("Text",-font=>"{arial} 12 {bold}")->pack(-side =
+> 'bottom', -fill => 'both', -expand => 1);
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i.e. global to the file so these statement later

for($t=0;$t<$lthree;$t++)
 {
 if($mpart=~/$three[$t]/)
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caused the problem.Here I had declared $t without "my".This portion of code was earlier in a separate
file.I did not notice this bit earlier.
Thanx :)