title: couldn't compile regular expression pattern: quantifier operand invalid error when trying to substring in tcl with regexp
body: <p>I have a string like <code>ED-SNC::SNC0-1-2:101:::RTEOPR=REGROOM,TYPE=DYNAMIC</code> and I want to get the <code>TYPE=DYNAMIC</code> from it and save it in a variable.
  I do <code>set editParam [regexp $line {(?&lt;=,).*$}]</code> and I get error:</p>
  
  <p>couldn't compile regular expression pattern: quantifier operand invalid
  what am I missing here?</p>