The way you have defined the array doesn't looks correct to me. If you are talking about an array

my @array = ("PSTR_0", "PSTR_1",   "PSTR_2","PSTR_3","PSTR_4", "PSTW_0
+","PSTW_1","PSTW_2","PSTW_3","PSTW_4",
"PWWD_3","PWWD_2","PWWD_1","PWWD_0");
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then have a look to my program. I think it will give you what you have asked.

#!/usr/bin/perl

use strict;
use warnings;

my @array = ("PSTR_0", "PSTR_1",   "PSTR_2","PSTR_3","PSTR_4", "PSTW_0
+","PSTW_1","PSTW_2","PSTW_3","PSTW_4",
"PWWD_3","PWWD_2","PWWD_1","PWWD_0");
            
my @PSTR = (grep{m/PSTR_\d/}@array);
print @PSTR,"\n";

my @PSTW = (grep{m/PSTW_\d/}@array);
print @PSTW,"\n";

my @PWWD = (grep{m/PWWD_\d/}@array);
print @PWWD,"\n"
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