It reminds me on patern ranges in awk. Could anyone explain what's going under the hood of this code?

There's no need to; perldoc perlop explains it nicely already:

     In scalar context, ".." returns a boolean value.  The
     operator is bistable, like a flip-flop, and emulates the
     line-range (comma) operator of sed, awk, and various
     editors.
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-sauoq
"My two cents aren't worth a dime.";

E:\>perl -MO=Deparse,-p -ne"print if 15 .. 17 "
LINE: while (defined(($_ = <ARGV>))) {
    ((15 .. 17) and print($_));
}
-e syntax OK

E:\>perl -MO=Deparse -ne"print if 15 .. 17 "
LINE: while (defined($_ = <ARGV>)) {
    print $_ if 15 .. 17;
}
-e syntax OK
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If the POD explanation isn't enough, it wasn't for me having never used sed or awk to any great extent, then this might clarify things.

perl -e"open ARGV,'<',$ARGV[0]or die $!; while(<ARGV>){ print if $. >=
+15 and $. <=17 }" file
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This is (roughly) analogous to the one-liner you showed except it will only handle a single input file. The open and while parts are performed for you by the -n command line switch. See perlrun for details.

The 15 .. 17 is (roughly) equivalent to the if condition above.