use strict;
use warnings;

sub scramble {
    lc $_[0] =~ s{(^.{$_[1]}|.{$_[1]}$)}
      {join '', (split '', $1)[map -$_, 1..$_[1]]}reg;
}

print scramble( "Institute", 3 ), "\n";
print scramble( "Babraham", 2 ), "\n";