use strict;

my @list=('xxxxxa : yyyyy blah blah','xxxxxb : yyyyy blah blah','   ','xxxxxc : yyyyy blah blah',': this is strange','xxxxxd : yyyyy blah blah',"\n",'xxxxxe : yyyyy blah blah');

my @result = map {m/(.*?)\s+:/} @list;

print join("\n",@result);