if( $var eq ' ' x length($var) ) {...}

##</code><code>##

if( $var eq map tr/A..Za..z0..9/ /, $var ) {..}

##</code><code>##

if( $var eq map tr/\000..\277/ /, $var ) {..}

##</code><code>##

if($var  eq join '', map{ tr/\000..\177/ /c; $_; }  split '', $var ) {...}