C:\test>type 577397.dat
"1"
{
"data1" "test.V1_0";
"StrCatDone" "0";
"seq_name" "sequence.V5_0";
"seq_step" "22";
}
"2"
{
"data1" "test.V1_0";
"StrCatDone" "1";
"seq_name" "sequence.V5_0";
"seq_step" "41";
}

## Note: This should be typed as one line but is wrapped for posting.
## On *nix system, you'lll need 's instead of "s.

C:\test>perl -0175 -i.bak 
-pe"/StrCatDone. .1./ and s/sequence.V5_0/sequence.V6_3/" 
577397.dat

C:\test>type 577397.dat
"1"
{
"data1" "test.V1_0";
"StrCatDone" "0";
"seq_name" "sequence.V5_0";
"seq_step" "22";
}
"2"
{
"data1" "test.V1_0";
"StrCatDone" "1";
"seq_name" "sequence.V6_3";
"seq_step" "41";
}