Just declare my @xxx once.

my $op = "numbers"; # for example
 
my @xxx = qw(one two three) if ( $op eq "numbers" );
@xxx = qw(four five) if ( $op eq "alpha" ); 
@xxx = qw(six ten) if ( $op eq "alp" );

print "@xxx\n";
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results in: one two three

A.A.