The problem is that 'use' statements get wrapped in BEGIN blocks, so $pathtolib isn't set by the time 'use lib' needs it. Here's how you can accomplish what you're looking for:

#!/usr/bin/perl
my $pathtolib;
BEGIN { $pathtolib = &opentextfile; } # opentextfile must be defined b
+efore this line
use lib $pathtolib;
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or even:

#!/usr/bin/perl
# define opentextfile somehow
use lib &opentextfile;
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