Do I understand correctly that the variables named *_L1_* are lower limits and *_U1_* are upper limits? Although pme has shown code very similar to what I was thinking, the key thing to note is that you can restructure your $FEB_L1_W1 variables into a hash, and then see the similarity in the data structures (Data::Dumper or Data::Dump can also be helpful here).

my %months = (
    FEB => { W1 => 11.14,
             W2 => 11.22, },
    MAR => { W1 => 33.17,
             W2 => 44.44, },
    APR => { W1 => 55.00,
             W2 => 66.66, },
);
my %limits = (
    FEB => { W1 => { L1 =>  11,    U1 =>  12.05 },
             W2 => { L1 =>  13.06, U1 =>  13.06 }, },
    APR => { W1 => { L1 =>   1,    U1 =>  20    },
             W2 => { L1 =>  33,    U1 =>  13.02 }, },
    MAR => { W1 => { L1 => -12.05, U1 => -14.0  },
             W2 => { L1 =>  22.0,  U1 => -13.02 }, },
);
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And then notice you can create loops to loop over both at the same time, like in the following. Note I've made a few assumptions, like that limits for a certain month may not exist, but when they do, both the keys U1 and L1 are defined. If your input data varies, you may have to adjust this.

for my $mon ( sort keys %months ) {
    for my $week ( sort keys %{ $months{$mon} } ) {
        if ( exists $limits{$mon} && exists $limits{$mon}{$week} ) {
            my $value = $months{$mon}{$week};
            my $upper = $limits{$mon}{$week}{U1};
            my $lower = $limits{$mon}{$week}{L1};
            printf "%6.2f <= %6.2f <= %6.2f - ",
                    $lower,  $value,  $upper;
            if ( $value >= $lower && $value <= $upper ) {
                print "OK\n";
            }
            else {
                print "NOT ok\n";
            }
        }
        else { warn "No limits for month $mon / week $week\n" }
    }
}
[download]

Which gives the following output. Note I tweaked the input slightly to give at least one "OK" output.

  1.00 <=  55.00 <=  20.00 - NOT ok
 33.00 <=  66.66 <=  13.02 - NOT ok
 11.00 <=  11.14 <=  12.05 - OK
 13.06 <=  11.22 <=  13.06 - NOT ok
-12.05 <=  33.17 <= -14.00 - NOT ok
 22.00 <=  44.44 <= -13.02 - NOT ok
[download]