If the order of the values is important and the keys not then maybe use a hash of arrays (HoA)

#!perl
use strict;

my @routers = ( "R0", "R2", "R3" );

my %fpc =  (
  R0 => [5,4], 
  R2 => [3,2],
  R3 => [1,0],
);

my %pic =  (
  R0 => [5,4], 
  R2 => [3,2],
  R3 => [1,0],
);

for my $r (@routers) {
  print "value of r is $r\n";
  for my $f (@{ $fpc{$r} }) {
    for my $p (@{ $pic{$r} }) {
      print "request chassis pic offline fpc-slot $f pic-slot $p\n";
    }
  }
}
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