Is there a reason that .str.split() will not work with '$_'? : <p>I am trying to split a string using .str.split('$_') but this is not working. </p>

<p>Other combinations like 'W_' or '$' work fine but not '$<em>'. I also tried .str.replace('$</em>') - which also does not work.</p>

<p>Initial string is '$<em>WA</em>:G_COUNTRY'</p>

<p>using 
ClearanceUnq['Clearance'].str.split('$_')
results in [$<em>WA</em>:G_COUNTRY]
no split.... </p>

<p>whereas 
ClearanceUnq['Clearance'].str.split('$')
results in [, <em>WA</em>:G_COUNTRY] 
as expected</p>
