#!/usr/bin/env perl  or #!/usr/bin/perl
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Why do you use these instead of specifying the exact Perl version you want to run?

Just use

#!/home/deafskeptic/perl5/perlbrew/perls/perl-5.20.1/bin/perl -w
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That way you are explicit about the Perl version.

You will have to (re)install all Perl modules with the new Perl version.