10
11
10
11

12
11
10
11

sed 's/10/12/' file1 >file2

awk '!changed && /10/ { sub(/10/, "12"); changed = 1}1' file1
12
11
10
11

sed '0,/10/s/10/12/' file1 >file2

sed '0,/10/ s/10/12/' file1 > file2

echo | cat - file | sed '1,/10/s/10/12/; 1d'

sed '1,/10/s/10/12/; 1d' << EOF

$(cat file)
EOF

sed '1,/10/s/10/12/; 1d' <(echo; cat file)