you could use concatenation ("the dot operator") : 
my $crypticString="LR20SR37PD30LR23CR23BT01H";
my $acceptableLength=40;
my $paddedString =$crypticString . " " x 
    ($acceptableLength - length ($crypticString));
print "'$paddedString'";

[download]
Also, using \s to indicate " " might be confused with the character class \s (which also includes newlines and tabs).

In reply to Re: Padding with \s by boo_radley
in thread Padding with \s by Anonymous Monk

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