Use eq instead. :)

my $input = shift;
if($input eq $scalar)
....
[download]

If you really want a regexp for this though, you can use ^ and $ like this:

$string =~ /^user1$/;
[download]

^ matches only at the beginning of the string, and $ only at the end, so this way you force it to match only if it matches the whole string.

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It is pitch black. You are likely to be eaten by a grue.