Although ysth has a fix for the following issue, be careful using !/$position/ when grepping to remove unwanted elements, as unintended results may happen:

use strict;
use warnings;

my @priority = qw(RB1 RB2 FL1 FL11 FL2 QB1 QB2 TE1 WR1 WR2 DST);
my $position = 'FL1';

print "$_\n" for grep !/$position/, @priority;
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Output:

RB1
RB2
FL2
QB1
QB2
TE1
WR1
WR2
DST
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Note that elements 'FL1' and 'FL11' were removed. To avoid this, use either ysth's $_ ne $position or !/^$position$/ (which forces a complete--not just partial--match) when grepping in your script.