If you only want to look up exact matches, you may want to stick the lookups in a hash rather than using substitutions in a subroutine (you might use your subroutine to access the hash instead). Maybe something like this?
my %interpret = (
'43 F' => 'Tunnel 1/2 Hr FT',
'43 P' => 'Tunnel 1/2 Hr PT',
'45 F' => 'Tunnel No Lunch FT',
'45 P' => 'Tunnel No Lunch PT',
'F' => 'Full Time No Clock',
'O' => 'On Call No Clock',
'P' => 'Part Time No Clock',
'T' => 'Temporary No Clock',
);
my $result = "43 P"; # comes from somewhere else
my $interpretation = $interpret{$result};
print $interpretation;
-- Mike
--
just,my${.02}