4.9 configure error etch debian flex not found

[Mark Lewis]

Hello list

# ./configure
...
checking for flex... no
checking for lex... no
configure: error: monit requires flex, not lex

Checked the archives for this error couldnt see similar - just  
thought I'd check with you guys before I searched for and installed  
flex - can someone tell me why I need this installed to install  
monit?  Almost everything else I've installed configures no problem  
and monit looks rock solid.  Anyone else had this problem experienced?

Thanks
Mark