perl - Use sed to replace word in 2-line pattern -

i try use sed replace word in 2-line pattern word. when in 1 line pattern 'macro "something"' found in next line replace 'block' 'core'. "something" put reference , printed out well.

my input data:

macro abcd   class block ;   symmetry x y ; 

desired outcome:

macro abcd   class core ;   symmetry x y ; 

my attempt in sed far:

sed 's/macro \([a-za-z0-9]*\)/,/  class block ;/macro \1\n  class core ;/g' input.txt 

the above did not work giving message:

sed: -e expression #1, char 30: unknown option `s' 

what missing?

i'm open one-liner solutions in perl well.

thanks, gert

using perl one-liner in slurp mode:

perl -0777 -pe 's/macro \w+\n  class \kblock ;/core ;/g' input.txt 

or using streaming example:

perl -pe '     s/^\s*\bclass \kblock ;/core ;/ if $prev;     $prev = $_ =~ /^macro \w+$/   ' input.txt 

explanation:

switches:

• -0777: slurp files whole
• -p: creates while(<>){...; print} loop each line in input file.
• -e: tells perl execute code on command line.