my @LINES =<IN>;
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This reads all the lines, and stuffs them into @LINES.

while(<IN>){
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You've already read all the lines! What do you expect to read now?

my @fields = split ';', $_;

I thought you said it was a tab delimited file?

if ( $fields[8] =~ /^[sno]/ =~ /^[sno]/ ) {
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What are you trying to do here? If you want to know that there is a value for sno, do something like:

if ($fields[8] =~ /(?:^|;)sno=[^;]/) { ... }
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And if you have a string literal, there is really no need to backslash all your spaces (unless it's the literal is a regexp pattern under the /x modifier, and you want the regex engine to see the spaces). Your print statement will be much more readable if you get rid of them.