if ($x =~ /^(?:${\join "|", $y-1 .. $y+1})$/)

##</code><code>##

$ perl -E 'my $y = 3; say "$_: ", /^(?:${\join "|", $y-1 .. $y+1})$/ ? "YES" : "NO" for 1..5'
1: NO
2: YES
3: YES
4: YES
5: NO

##</code><code>##

if ($x==$y or $x==$y-1 or $x==$y-2 or $x==$y-3 or $x==$y+1)

##</code><code>##

if ($x =~ /^(?:${\join "|", $y-3 .. $y+1})$/)

##</code><code>##

$ perl -E 'my $y = 3; say "$_: ", /^(?:${\join "|", $y-3 .. $y+1})$/ ? "YES" : "NO" for -1..5'
-1: NO
0: YES
1: YES
2: YES
3: YES
4: YES
5: NO