$string = "H e l l o  P e r l p r i n t";
print $string for $string =~ s/\b[ ]//g; 
print $string for $string =~ s/[ ]\b//g;


UPDATE:added non-capturing square brackets to account for more efficiency after
 Anomalous Monk's enlightenment... 

##</code><code>##

Hello PerlprintHelloPerlprint