>>> s = 'Stack Overflow - Ask Questions Here'  
>>> s.split(' - ')  
['Stack Overflow', 'Ask Questions Here']  
>>> # To get the substring before the match  
>>> s.split(' - ')[0]  
'Stack Overflow'
	
>>> import re
>>> re.split(' - ', s)[0]
'Stack Overflow'
	
$sentence = 'Stack Overflow - Ask Questions Here';

if ($sentence =~ /^(.*?) - /) {
  print "Found match: '$1'n";
}
	
$sentence1 = 'Stack Overflow - Ask Questions Here - And more here';
$sentence2 = 'Just Stack Overflow';

$sentence1 =~ /^(.*?)( - |$)/;
print $1, "n";

$sentence1 =~ /^(?|(.*) - |(.*)$)/;
print $1, "n";

$sentence2 =~ /^(.*?)( - |$)/;
print $1, "n";

$sentence2 =~ /^(?|(.*) - |(.*)$)/;
print $1, "n";