c:\> perl -n -e "print if /^PARTNAME/ && /PARTNAME$/ && $last; $last = /^xyzdf/ && /xyzdf$/ ? $_ : ''" file1>file2
# file2:
#PARTNAMEhjjhhjhjkjkjkjkjPARTNAME
#PARTNAMEhjjh88888888888jkjkjkjkjPARTNAME
#PARTNAMEhjjh8888iiiiiiiiiiiii888jkjkjkjkjPARTNAME

##</code><code>##

xyzdf
PARTNAMEXXXXPARTNAME

##</code><code>##

c:\> perl -n -e "print if /^PARTNAME/ && /PARTNAME$/ && $last; $last = /^xyzdf/ && /.xyzdf$/ ? $_ : ''" file1>file2