if ( $FileExt eq '.xlsx' || $FileExt eq '.pdf' )
    { print "Match!\n" }

if ( $FileExt =~ /^\.(?:xlsx|pdf)$/ )
    { print "Match!\n" }

use Quantum::Superpositions;
# OR
#use Perl6::Junction qw/ all any none one /;

if ( $FileExt eq any('.xlsx','.pdf') )
    { print "Match!\n" }