Just put $pattern in the match e.g 
## remove regex-unfriendly newline
chomp( my $pat = <STDIN> );

open(FILE, "filename") or die("ack: $!");

while(<FILE>) {
  print
    if /$pat/;
}

[download]
That will get a line of user input, loop over FILE and print if a given line matches $pat. Because regexes are interpolated the $ of $pat isn't interpreted as the meta-character $, but is interpolated into the regex match. See. perlop and perlre for more information on regexes and their quoting behaviour.
HTH

_________
broquaint

In reply to Re: Pattern matching against a variable by broquaint
in thread Pattern matching against a variable by bonoboy

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